Windows XP crashed, please help

I've got a serious problem. I installed windows XP sp3 on my friend's pc. First it couldn't format it, just reinstall windows files, all other program files left sitting there. Then I installed on the D disk. So I installed Partition Magic hoping I can make D primary and C secondary so I can format C disk...

Now thats when the problem occured. I saved changes in Partition Magic, and it said that i restart. I restarted my pc and (unusually) started "Boot from CD..." and before it didnt even say that, I couldnt boot from anything on xp startup, only from my computer directly through the CD.
Now I couldnt remove that boot from CD, and xp couldnt start, so I went to Setup of the BIOS etc and accidentaly changed some of the CPU settings, like Max memory clock and stuff...

Now we hit the Power On button and the screen is black, nothing moving...

I need serious help about this.
Nothing got burned or crashed, just the settings got ****ed up, so I only get a black screen.

Pls can you direct me through a right way, some application that can be put into the CD/DVD Rom and it would start it..

You havent told us brand and model. But.
There is not a quick fix after all that has happened... no disc... no software... unless you can go back to an earlier restore point. Without a couple of good restore points, you would likely best be served by using a new hard drive or used drive you can reformat, to install WXP SP3. Then migrate the working files and folders off this damaged drive. It will save you hours and hours of patch and fix that may make it worse before it gets better.
Be sure to do new installs of software, rather than drag and drop, for best results.